Breathless through Time: Oxygen and Animals across Earth's History

Area of Science:

• Paleontology
• Geochemistry
• Marine Biology

Background:

• Earth's oxygen levels have fluctuated dramatically, impacting marine ecosystems.
• A link between oxygen availability and animal diversity has been proposed, particularly around the Cambrian explosion.
• Past oxygen changes offer insights into modern climate change impacts.

Purpose of the Study:

• To examine the co-evolutionary relationship between oxygen levels and marine animal diversity throughout Earth's history.
• To understand the impact of past oxygenation events and deoxygenation on marine life and extinction rates.
• To draw parallels between ancient environmental stressors and modern anthropogenic global change.

Main Methods:

• Analysis of the geologic record to reconstruct past atmospheric and oceanic oxygen levels.
• Correlation of oxygen level changes with fossil evidence of marine animal diversity and extinction events.
• Comparative analysis of ancient large igneous province eruptions and their environmental consequences.

Main Results:

• Oxygen levels rose more gradually than previously thought, potentially crossing critical thresholds at lower concentrations during the Cambrian.
• Low to moderate oxygen levels in the early Paleozoic likely contributed to high metazoan extinction rates.
• Mass extinctions in the later Paleozoic and beyond are linked to ocean deoxygenation caused by volcanic activity, leading to warming, acidification, and hypoxia.

Conclusions:

• Ancient CO2 injections consistently trigger warming, acidification, and oxygen loss, mirroring modern environmental crises.
• Understanding past oxygen dynamics, including temperature-dependent hypoxia, is crucial for predicting future biosphere responses.
• Ecophysiological approaches are needed to calibrate the biosphere's response to environmental change across diverse scales.